Project Summary Ending the AIDS epidemic in sub-Saharan will require further engagement of men in HIV testing, prevention, and treatment, a challenging task given that nearly 50% of HIV-positive men in many countries are unaware of their HIV status and men have lower uptake of HIV antiretroviral therapy (ART) and pre-exposure prophylaxis (PrEP). This study focuses on a highly mobile population of men ? fishermen ? in Kenya?s Lake Victoria shoreline communities, where HIV incidence rates are extremely high. Two recent innovations ? HIV self- testing (HIVST) and social network-based interventions ? hold promise for overcoming barriers to HIV testing and linkage to services for both HIV-positive and HIV-negative men. This study seeks to determine if an HIV status-neutral, social network-based approach, along with low-cost incentives, can promote HIV testing, linkage to care and prevention, and better health outcomes in men. It will pursue three aims: Aim 1: Determine whether providing HIV self-tests to network-central men for distribution to other men in their close social networks increases men?s HIV testing uptake. We will conduct social network mapping in study communities in Siaya Country, Kenya to identify distinct close social networks of men. We will then randomize these social networks to intervention and control groups. Network-central, highly- connected men in each network will be recruited as ?promoters?, and receive HIVST training. Promoters in networks assigned to the intervention will then receive self-tests for distribution to men in their networks. Promoters in networks assigned to the control will instead distribute vouchers for free self-tests at nearby health clinics. We hypothesize higher HIV testing among men in networks that receive the intervention. Aim 2: Determine whether network-central promoters and small incentives can increase ART and PrEP uptake among men. We will test whether network-central promoters can enhance linkage to ART and PrEP after self-testing, thereby addressing a key limitation of HIVST. Promoters in the Aim 1 intervention group will be asked to distribute information and transport vouchers for ART or PrEP to men in their networks. Our primary hypothesis is that the intervention will result in higher rates of linkage to ART or PrEP (confirmatory testing and ART referral for positives, and PrEP screening for negatives). We also hypothesize higher ART and PrEP uptake within 3 months among men in social networks assigned to the intervention group. Aim 3: Test the impact of interventions on ART or PrEP retention and adherence. We will measure 6- and 12-month VL and tenofovir levels, using a recently-developed low-cost, point-of-care PrEP adherence urine immunoassay. Across all aims, we will use qualitative and mixed methods to identify the pathways of intervention action, and understand how social networks and incentives affect testing and ART and PrEP uptake and retention. This study promises high scientific and public health impact, by testing new approaches to improve the prevention and care cascades in high-risk, mobile men in high priority settings.